The disclosure relates to a circuit to supply energy to a sequential circuit of typically nonlinear loads using a current source. Preferably, the load comprises a series circuit of LEDs. This current-driven load, preferably a series circuit of LEDs, consists of one to N elements and should be partially short-circuited or dimmed.
Various energy supply circuits for LEDs or LED series circuits are disclosed in US-A-2012/223649, DE-A-10 2009 025 752, US-A-2012/153844, and US-A-2010/194274.
Each of the nonlinear loads that is connected in series typically has one switch connected in parallel. Each of these switches may be open and/or closed.
The resulting change in voltage now presents the problem that the current is a combination of the current of the current source and the changing voltage of an energy storage that is typically present, and thus it is no longer determined directly by the current source. Such a current source can be, for example, a current-controlled DC/DC converter.
Two cases result:
a The first case, namely the case CLOSED, relates to the closing or reduction in conducting-state DC resistance of one or more of the aforementioned switches: The resulting short-term increase in current can have undesired side effects going all the way to damaging the following load.
b The second case, i.e., the case OPEN, relates to the opening or the increase in conducting-state DC resistance of one or more of the aforementioned switches: Until a supporting energy storage has been charged to an increased energy content—in the case of a capacitor to an increased voltage—it is possible that no current or insufficient current is available for the increased load. This can temporarily limit the function. For example, the luminous intensity of an LED chain can noticeably decrease. However, as a rule if transients are short they are not perceived as loads by LEDs. But if the loads are motor phases or relays, an interruption in the current such as described could have undesired side effects.